Along with a general decline in overall health, most chronic degenerative human diseases are inherently associated with increasing age. Age-associated cognitive impairments and neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, are potentially debilitating conditions that lack viable options for treatment, resulting in a tremendous economic and societal cost. Most high-profile clinical trials for neurodegenerative diseases have led to inefficacious results, suggesting that novel approaches to treating these pathologies are needed. Numerous recent studies have demonstrated that senescent cells, which are characterized by sustained cell cycle arrest and production of a distinct senescence-associated secretory phenotype, accumulate with age and at sites of age-related diseases throughout the body, where they actively promote tissue deterioration. Cells with features of senescence have been detected in the context of brain aging and neurodegenerative disease, suggesting that they may also promote dysfunction. Here, we discuss the evidence implicating senescent cells in neurodegenerative diseases, the mechanistic contribution of these cells that may actively drive neurodegeneration, and how these cells or their effects may be targeted therapeutically.